Boring-tool



L. P CROSMAN.

' BORING TOOL.-

. APPLICATIQN FILED FEB. 20. I919- I Patented Dec. 14, 1920.

2 SHEETS-SHEET 1- A TTORNE Y8 L. P. CROSMAN.

BORING TOOL.

A P P L l C A T O N F L E D F E B 2 0 I I 9 I 9- 1,362,477. Patented Dec. 14,1920.

MEETS-SHEET 2? WHEN TOR A Aria/mars UNITED, s rEsr ENT OFFICE.-

LORIN G PICKERING CROSCMAN, 0F PORTLAND, MAINE.

BORING-TOOL.

S ecification of Letters Patent.

Patented Dec. 14, 1920.

Application filed February 20, 1919. Serial No. 278,113.

To all whom it may cone-cm:

.rie it known thatl, LoRINo P. CRosMAN,

- a citizen of the United States, and a resident of Portland, in the county of Cumberland bodying the invention;

Fig. 2 is a side elevation taken at right angles to Fig. 1;

Fig. 3 is a top plan view;

Fig. 4 is a bottom plan view; l iig. 5 is a central sectional view of the too Fig. 6 is a sectional View taken horizontally on the line 6-6 of Fig. 1 of the drawings,

Fig. 7 is a perspective view of the tool tilted upwardly so as to show the curvature of the body at one side, the blades or bits being omitted: and

Fig. 8 is a perspective view looking toward the bottom of the tool and one side.

The tool shown in the drawings for the purposes of illustration comprises a head 1 with a shank 2 and cutting blades or bits 8, 3 secured to the head. The head presents sufficient portions of a surface of revolution to provide bearing surfaces of rounding or convex formation as shown at 11, and, as

shown, this head is of general hemispherical configuration, being in the form of a solid member or casting cut away at opposite sides to provide clearance for chips. The head is provided with seats 5, 5 at its end to receive the inner ends of the bits 3, 3; and, with seats 4, 4 at opposite sides of the head to receive the outer ends of said bits. bits are secured rigidly in said seats by screws 7, 7 and 8, 8.

The surface of the head at the portions 11 serves as a shoe in the operation of the tool, and the cutting edges of the bits 3, 3 project slightly beyond the face of said shoes to cut the material being bored, the operation being similar to that of a plane, the depth of the bit edges beyond the shoe sur- The faces determining the depth of cut. The head is cut away spirally inwardly beneath and to the rear of the hits, as indicated at 9, 9, to provide clearance for chips. In order to prevent slipping and to maintain the tool accurately centered during the operation thereof, a pilot centering point 10 is provided, the same being secured in the head axially and the blades 3 being recessed 'at their overlap ping portions to accommodate the centering point therebetween. Such centering point may be formed to provide cutting edges if desired, especially if the too]. is to, be used for cutting hard material.

' The blades or bits 3' are provided with the cutting edges 00 disposed at the inner edges thereof and terminating at the pilot centering point 10, beyond which said blades have their inner edges inset. The cutting edges are offset from the face of the head except at the upper and lower ends thereof, and the intermediate portions thereof are spaced from the adjacent edges of the convex or rounding portions 11 of the head 1, so as to provide slots through which the chips are. discharged into the cut away portions of the head at the opposite sides thereof to escape at the top, which is open at both sides, as

will be clearly apparent from an inspection of the drawings.

The bits 3 are preferably of spiral shape,-

in order that a portion at least of the cut may be in effect a drawing cut, and, as shown, the cutting edge extends forwardly at portions more removed from the center of the tool, such form operating with less tendency to cause splintering when cutting across the grain.

It is to be understood that the form of head shown is merely illustrative and that various modifications may be made without departing from the principle of providing a rotary head presenting exteriorly a surface of revolution having an axis coinciding with the axis of the tool.

Having thus described my invention, I

claim as new and desire to secure by Letters Patent:

r 1. A boring tool of the character described comprising a rotary head and flat spiral bits secured thereto and extending from the end thereof outwardly and rearwardly along the surface of said head, the head being cut away beneath and to the rear of said bits toprovide clearance for chips.

2. A boring tool of the character described comprising a rotary head in the form of a solid member or casting, spiral bits secured thereto and extending from the end thereof outwardly and rearwardly along the surface of said head, the head being cut away beneath and to the rear of said bits to provide clearance for chips, and a centering point at the forward end of said head to center the tool in operation.

3. A tool of the character described com- .prising a substantially hemispherical head faces of the head determiningthe depth of cut of thetool.

4:. A boring tool of the character described comprising a substantially hemispherical head having recesses and spiral bits secured to said head in said recesses and extending along the surface thereof but having cutting edges projecting radially beyond the surface of the head a distance equal to the depth of cut desired.

5. A boring tool of the character described comprising a substantially hemispherical head having overlapping recesses at the center thereof and'spiral bits secured to said head with ends in said recesses; overlapping and extending along the'surface thereof but having. cutting edges projecting radially beyond the surface of the head a distance equal to the depth of cut desired, the cutting edges of said bits being advanced forwardly at the ends removed from the center of the head to provide a drawing out in use.

6. A boring tool of the character described comprising a substantially hemispherical head, spiral bits secured to said head in partially overlapping relations and extending along the surface thereof but having cutting edges projecting radially beyond the surface of the head a distance equal to the depth of cut desired, the cutting edges of said bits being'advanced forwardly at the ends'removed from the center of the head to providea drawingcut in use, and a pilot centering point at the forward end of said head between said overlapping portions.

7. A boring tool of the character described comprising a head and curved cutting blades secured thereto,-said blades substani y" eti g-v at.v t e d.- O he h ad conformity with the surface thereof and extending radially outward and backward to conform to the shape of the head, the head being cut away to provide clearance for chips. p v

8. A boring tool of the character described comprising a head of substantially hemispherical shape, and curved knives secured to said .head, substantiallyv meeting at the end of the head and extending radially outward and backward along the surface of the head, the cutting'knives projecting radially slightly beyond the curved face of said h ad. J j

- 7 Lemma, PICKERING cizosmu. 

